1. Field of the Invention
The present invention relates to compositions which are useful for purifying turbid and/or polluted water to clarify and make such water suitable for drinking. In particular, the present invention is directed toward a formulation and use thereof which is advantageously formulated for purifying small quantities of water for personal use, such as would be necessary in emergency situations encountered by campers, military personnel and other who find themselves in a situation where the only drinking water available is contaminated with turbidity causing materials and other pollutants.
2. Background of the Invention
Various types of water purification ingredients are known for removing particular types of pollutants from water. Typically, such ingredients are utilized in large scale water purification facilities to remove specific pollutants encountered in a particular source of water. For example, flocculants or coagulants are known to be useful for removing particulate contaminants found in some sources of water before such water can be discharged into a lake or stream. Likewise, various types of adsorbants are available for removing certain types of pollutants.
Typical procedures for using conventional water purification chemicals require operation under carefully controlled conditions and generally involve operation of expensive equipment which can be complicated to operate. The useful chemicals for purifying the water are generally not combined with each other since they typically require conditions during the purification process which may not be suitable for the other ingredients. Thus, many operations require sequential use of each ingredient as needed and the physical conditions for each sequential step are adapted to meet the functional or physical limitations of each ingredient.
In some instances a combination of ingredients has been formulated into a single composition. However, the combination of ingredients in these compositions is very limited and such compositions are often in a physical form which makes them unsuitable for convenient use under typical field conditions encountered by campers, military personnel, etc. Furthermore, such compositions are not complete for purifying water and they thus require additional materials and process steps for acceptable clarification and removal of pollutants. In addition, such compositions often require a long processing time which is impractical for certain applications, especially military applications where the need to quickly provide potable water may be critical.
In order for a water purification composition to be suitable for field applications in which water can be clarified and made pollutant free, such a composition should be effective in a small quantity, have a long shelf life and be in a solid dry form for easy packaging and convenient use and operable under a wide range of environmental conditions. More importantly, such a composition should contain all of the effective ingredients in a single composition and such ingredients should be formulated in a manner so that they do not interfere with one another. In addition, the individual ingredients should be quickly dispersible when placed into water so that the composition is quickly activated. It is also very important that the composition can purify and clarify the water quickly.
Prior art compositions have never contained all of the essential ingredients in a single composition for water purification because of certain obstacles associated with making such a combination of ingredients. In particular, it has never been possible to combine all of the essential ingredients in a single composition because the individual ingredients tend to interfere with one another when blended together. Also, from a theoretical point of view, the chemical characteristics of the individual ingredients suggests that such a combination would not be possible if you expect each ingredient to function without interfering with each other in purifying the water.
Currently nothing exists on the market for manual purification except for I.sub.2 tablets which are only effective as a biocide. These tablets do not clarify or sorb metals or organics unless filters or other mechanical devices are employed. Even then broad range pollutant removal is incomplete.
U.S. Pat. No. 2,345,827 (Olin) teaches clarification of water using bentonite clay. The clay must first be formed into a slurry with water and then the slurry is added to the water to be purified. When forming the slurry, care must be taken to avoid ionizing substances or coagulants. Thus, Olin teaches against incorporating a coagulant into the slurry. Small amounts of ionizing substances or coagulants are tolerated for forming the slurry, but the amount is limited to an amount normally found in water. In rare instances, where insufficient ionizable substances are found in water being purified, then these substances may be added to the water being purified, either before or after addition of bentonite slurry to the water. However, the coagulants or ionizing substances must not be added to the bentonite slurry before it is added to the water. Thus, Olin goes to great lengths to avoid combining a coagulant with the clay in a single composition which is to be added to the water. Thus, Olin fails to provide a complete composition for purifying the water. Furthermore, Olin's slurry is inconvenient to use in the field.
U.S. Pat. No. 3,524,811 (Tsuk) discloses the use of certain polymeric flocculants to promote settling of solids suspended in water. Tsuk emphasizes that when two treating agents are combined, they are formulated into an acid solution having a pH below 3. Such a harsh pH would be expected to interfere with zeolites which require a pH of 6-11. Thus, Tsuk's composition effectively precludes the use of zeolites therein. Furthermore, Tsuk does not provide a convenient dry formulation which could quickly remove all of the pollutants from water.
It has been noted by Bacon in U.S. Pat. No. 3,350,304 that bentonite, especially expandable or swellable bentonite should be avoided in a coagulant composition which is used for flocculating finely divided solids in water. Bacon observes that bentonites are associated with an undesirable carry-over of colloidal material into the filter bed.
Bentonite clay has been combined with polymeric flocculants in the composition described in U.S. Pat. Nos. 3,388,060 (Clark); 3,338,828 (Clark); 3,130,167 (Green); 4,415,467 (Piepho); 4,332,693 (Piepho); and 4,765,908 (Monick). However, none of these compositions have overcome the problems associated with a complete combination of essential water purification ingredients and thus these compositions fail to provide a single formulation having the characteristics described above which are necessary for personal water purification in the field. In particular, none of these patents use attapulgite clay and zeolite to clarify and remove pollutants from water in a single composition. Furthermore, none of these patents include a biocide which is compatible with the other ingredients.
Attapulgite clay is known for use in water purification procedures. For example, U.S. Pat. No. 4,116,828 (Sawyer) discloses a water purification method which uses attapulgite clay and sepiolite. However, the clay does not result in clarification and, in fact, it contributes to turbidity. Consequently, cumbersome sedimentation and/or filtration techniques must be employed to remove the clay or sepiolite from the water.
Attapulgite clay is used in a coagulating agent described by Cocks in U.S. Pat. No. 3,342,742. Cocks uses the attapulgite clay and a nucleating agent which is impregnated in an alkali metal aluminate coagulant. Thus, the clay, being impregnated in the coagulant, cannot be freely dispersed in the water for effective removal of contaminants.
Zeolites have been described for use in water purification in U.S. Pat. Nos. 1,793,670 (Borrowman) and 2,004,257 (Tschirner). However, neither of these patents suggest how the zeolite can be combined with other essential ingredients to form a complete water purification composition wherein the numerous ingredients do not interfere with each other.
U.S. Pat. Nos. 3,860,526 (Corbett); 4,450,092 (Huang); 4,610,801 (Matthews); and 4,746,457 (Hassick) describe various types of materials which are suitable for treating water. An article published in Chemical & Engineering News entitled "Water Treatment Chemicals: Tighter Controls Drive Demand"; Mar. 26, 1990, use an overview of chemical technology involved in water purification. However, these references also fail to disclose a single convenient composition having all the necessary ingredients for making polluted water suitable for drinking and which can be quickly used in the field.
It is also known to use a biocide in water treating compositions to kill germs. However, bentonite and attapulgite clay contain water of hydration which is known to interact with biocidal materials such as chlorine dioxide. For example, a well known biocidal material is available which contains chlorine dioxide stabilized on diatomaceous earth. This biocide would ordinarily be considered to be an excellent biocide for use in drinking water because no toxic by-products exist after hydrolysis in water. However, even though bentonite is capable of removing diatomaceous earth, contact with the bentonite liberates chlorine dioxide even in dry formulations. The liberated chlorine dioxide would degrade organic flocculants and coagulants. Furthermore, the biocide will be spent prior to use thus giving the composition a short shelf life. For these reasons, effective compatible biocides have not been formulated with a single complete water treating composition which has a long shelf life which does not produce products which are toxic to humans.
Chlorine and iodine releasing biocides are also avoided in complete water treating formulations because chlorine and iodine ions readily react with a wide variety of organic compounds. Thus, these ions are avoided in compositions containing polymeric flocculants since the latter would be expected to become inactive in the presence of chlorine or iodine ions.
Clays also present certain problems with respect to compatibility with other ingredients. For example, bentonite clay and attapulgite clay are known to have exchangeable cations (Mg, Ca and NH.sub.4.sup.30) in their lattice structure. These ions would be expected to interfere with the proper functioning of zeolite, if zeolite is added to remove toxic metals and the like from the water. Also, since bentonite and attapulgite clays both develop negative charges, it would be expected that the bentonite would not function to remove the attapulgite clay from the solution because of expected repulsive forces between the two like-charged materials. Furthermore, attapulgite clay is known to be a powerful sorbant of polar organic materials due to its fine particle size and porosity. Thus, it would be expected that attapulgite would effectively sorb organic polymers such as organic flocculants and coagulants and thereby render them inactive. Thus, one would avoid combining attapulgite clay with polymeric flocculants and coagulants, especially adsorbed on a dry formula.
Typically, polymeric flocculants and coagulants require predissolving them in water or at least further dilution before adding them to the water. The predissolution is required to fully hydrate or expand the polymer molecule before it is added to the system to which flocculation or coagulation is desired. Mixing is required to accomplish the desired predissolution and when mixing solid polymers, 30-60 minutes or more is recommended. Thus, use of these polymers in solid dry form would not be expected to be useful for effective water purification, especially purification which can be quickly accomplished.
It is also known that bentonite clay in dry form should not be added to the water all at once since doing so results in the formation of a gelatinous blob which can only be broken up by vigorous stirring. Thus, it would not be expected that a complete water purification composition could be formulated with bentonite having all of the bentonite contained in the composition so that it does not have to be added to the water in more than one dose.
In view of the above, a long felt need remains in the art for providing a single dry formulation composition which can remove pollutants and turbidity and disinfect the water to make it safer for drinking.